This invention relates to a composition in a liquid used for removing a photoresist film such as made mainly of a novolak resin from a material and a method therefor in process of fabricating semiconductor integrated circuits and circuit substrates by use of a photoresist as a mask.
Generally, process for fabricating a semiconductor device includes sequential steps like that a photoresist is applied on a device surface to be patterned by exposure through a reticle or a photomask to form a photoresist mask for subsequent etching or ion-implantation process. Thus, the photoresist mask after use must be removed from the processed surface of the device by use of a remover.
The conventional remover for removing the used photoresist from the device is classified to an acid-based remover and an organic-based remover. Piranha where sulfuric acid:hydrogen peroxide=2:1 is a typical example of the former and the remover containing phenol is typical example of the latter. Recently, a remover including aminoethanol has been developed as a remover which belongs to the organic-based remover. This was reported by Laura Peters in SEMICONDUCTOR INTERNATIONAL, FEBRUARY, pages 58 to 64, 1992.
The conventional remover is, however engaged with some disadvantages as follows. Since the acid-based remover has a strong corrosion behavior, it cannot be used in case of contacting it with an aluminum wiring. On the other hand, sulfuric acid and hydrogen peroxide which are compositions of piranha is noxious.
If the remover containing phenol is used for removing the photoresist from the device, a substrate can not directly be rinsed by a pure water just after a step of removing the photoresist because the remover containing phenol is insoluble to water. Thus, it is necessary to rinse the remover remaining the device by use of a chlorophlorocarbon or organic chlorides solvent. After that, it is further necessary to rinse the used chlorophlorocarbon or organic chlorides solvent by methyl ethyl ketone or isopropyl alcohol before a final rinsing is carried out by pure water.
In this case, there are problems like that phenol which shows a strong toxicity of 5 ppm at an acceptable concentration is used and methyl ethyl ketone and isopropyl alcohol which are volatile organopotassium compound causing not only ozone layer destruction but also photochemical oxidant are used and discharged to the outside. In addition, the volatile organopotassium compound has a low flash point, for which there is a serious firehazard in using the volatile organopotassium compound. By the way, the flash points of methyl ethyl ketone and isopropyl alcohol are -5.6.degree. C. and 13.degree. C. respectively.
A remover mainly containing aminoethanol was developed to serve as the above mentioned remover. The remover containing aminoethanol, however, shows a stronger toxicity of 3 ppm at the acceptable concentration than that of phenol. In addition, aminoethanol shows a strong alkaline in aqueous solution, resulting in a corrosion action to metal such as the aluminum wiring formed on the device. Therefore, it is necessary to rinse the remover containing aminoethanol remaining on the device by other chemical substance before rinsing the device by use of pure water.